Process of making pulp for paper



Patented Mar. 31, 1925.

UNITED STATES 1,531,728 PATENT OFFICE.

GEORGE L. BIDWELL, OF RIEGELSVILLE, PENNSYLVANIA, ASSIGNOR TO THE WARREN MANUFACTURING COMPANY, OF RIEGELSVILLE, NEW JERSEY, A CORPORATION or NEW JERSEY.

PROCESS OF MAKING PULP FOE, PAPER.

No Drawing.

To all whom it may concern Be it known that I, Gnome L. BIDWELL, a citizen of the United States of America, and a resident of Riegelsville, in the county of Bucks and State of Pennsylvania, have invented a new and useful Process of Making Pulp for Paper, of which the following is a specification.

My invention relates to improvements in processes of producing pulp from hard stock for use in the manufacture of paper, and consists generally and broadly in dusting, cooking, and washing the hard stock in large pieces, in reducing such pieces, in

' bleaching and washing the reduced hard stock, and in keeping the latter in a state of hydration until the same is ready for the paper-making machine or said machine is ready for the pulp, all as hereinafter set forth.

The two more important features of my process reside in the utilization of comparatively large pieces of hard stock, or, in other words, in treating the stock in large pieces during a considerable period of the pulpmaking process. and in maintaining the stock ill;- a state of hydration until used, for reasons which presently will be made plain, and the steps in the process incident to producing or resident in said features are both, new and novel.

One object of my invention is to produce a hard-stock pulp, for use in the manufacture of paper, that can be handled in slush form, as in the manufacture of paper from soft stock, due to the fact that said pulp is maintained in an advanced stage or high state of hydration, to the end that a large and important saving is effected in time, raw material, power, labor, floor space, lime, bleach, etc. lVith this process complete control of the hydration of the fibres of the stock is both possible and practical, and any of the hard-stock elements can be rapidly converted into pulp which is suitable for either the coarse grades or the finest grades of coating, drawing, writing, map, ledger, bank-note, and similar papers, and ready at any time for the beater through which the pulp passes before it reaches the paper-making machine.

Another object is so to treat hard stock" with water and maintain the same in a state Application filed March 1, 1920. Serial No.362,825.

of hydration that the resultant pulp is thoroughly protected or preserved by a viscosity produced by the water in combination with the fibrous elements, and kept ready for instant use at all times. I control the hydration of the stock or fibre from the time the stock 1s cooked, or first washed, provided washing precedes the cooking, as may be the case, until said stock is run into the aper-making machine. And I do not sub ect the stock to pressure, or have to employ manual labor in the actual handling of the stock after the same is fed into the cooking and washing machine, which latter consists of an open-top engine preferably of the H01- lander type.

Still another object is to produce a hardstock pulp from which can be made a clean er paper than is possible with pulp produced by the old process or any modification of the same, and give to the finished paper superior characteristics that cannot be obtained under the old process. The aforesaid superior characteristics are due to the viscous bodies produced in the pulp by the long continued action of the water on the hard stock, to the action of said water on said stock throughout a number of steps in the process, and to the fact that hydration of the fibre is not permitted to become lost or even lessened.

A further object is greatly to simplify the hard-stock process and correspondingly to enhance or increase the efliciency and practicability of the same.

Other objects and advantages will appear in the course of the following description.

It is to be understood that some latitude is permissible in the number and order or sequence of the steps of the process, so long as the scope of what is claimed be not ex-' Old process.

l The old process of making paper or paper pulp from hard stock preliminarily consists 1n sorting, cutting, dusting, cooking, washing, bleaching and dralning. A mellow half stuff is thus produced which is allowed-to season in the drainer, and is then dug out, loaded into small hand-cars, carried to the beater engine, and furnished to the latter by hand. The steps of sorting consists in handling the hard stock to re-. move therefrom buckles, buttons, and all other foreign materials and substances. After the stock is sorted it is fed into a rag cutter and reduced to small pieces. The action of the rag cutter produces muchlint which represents a loss of fibre when the stock is sub'ected to the dusting step. The cut and r uced stock is led by an apron conveyor into what is termed a railroad duster, and thence into a cylinder duster. The purpose of the dusting operations produced by said dusters is to remove all the dust from the stock, and such purpose is most efi'ectually attained, but unfortunately the two machines take out with the dust and dirt a considerable quantity of lint, as just intimated, which represents a direct loss of stock, as much as 8% of the original weight of the hard stock being lost at this point.

From the cylinder duster the hard stock is led b another apron conveyor to a closed cooker 1n the form of a rotary boiler. This boiler is of either of the well-known cylindrical or s herical type, and mounted to rotate very s owly, or about three revolutions er minute. About three tons of stock may e placed in such boiler or cooker. 'As the charge of stock is aproned into the cooker, a cooking solution of caustic soda, milk or lime, or a mixture of lime and carbonate of soda is added. The cooker is then sealed, steam is admitted, the steam pressure being of from ten to forty ounds, and said cooker. is rotated for from t ree to fourteenhours, the cooking solution, the pressure of the steam, and the time of the cook all depending on the grade of paper that is to be made from the hard stock.

The large pieces of hard stock that I use in the new process could not be successfully cooked in the rotary boiler or cooker and in the manner inst explained, because such pieces would r0 1 up and would not cook.

After cooking the ard stock for the required length of time, the steam is shut off,

' and the cooker is blown to reduce the pressure so that said cooker can be opened. The

steam escapes through the customary blowoff, and a considerable amount of ood fibre passes off with the steam and .coo 'n llquor through said blow-ofi and is waste in spite of the presence of a strainer over the blow-off.

When the cooker is opened, by the removal of its man-heads, sald cooker is caused to revolve and the hard stock is automatically dumped on the fioor under the cooker, a certain amount escaping therefrom at each revolution. The cooker will not entirely empty itself in this manner, consequently the services of an attendant are required to pull the balance of the contents of the cooker, which is work of a very hot, diagreeable, and arduous nature.

The'hard stock is now permitted to cool and season, either under the cooker, or in a bin to which the entire cock is removed, the handling of the stock incident to the removal'thereof hastening the coolin of the same. The too sudden cooling of t e stock, however, makes it vegy and hard to bleach. fter seasoning, the stock is taken to a washing engine in small hand-cars, and thoroughly washed to remove all the dirt and residue of the liquor. .The washed stock is bleached to the desired degree of whiteness with chloride of lime or bleaching powder, after which all traces of the bleaching solution are removed by washing the stock in a drum washer. And the stock is finally discharged into cement or porous tile drainers which permit the water to drain oil. The stock is now known as half-stufi and is ready for the beating operation.

From the time the bale of hard stock is broken open until the half-stuff is dug from the drainer from four to ten days must elapse.

The old process involves a great amount diflicult to Washof labor, inasmuch as the stock has to be handled and rehandled at every stage or'step of the way, and handled and rehandled at a disadvantage. Such rocess is also very uneconomical because 0 the waste due to the fact that the fundamental principle of cleaning is wrong, and to'the-continuous or fre quent handling. Furthermore chemicals used in the cooking and bleaching steps of the process are wasted because of the crude manner in which they are applied. And most important of all is the loss sustained because of the partial hydration of the fibre, under the old process, and the loss of power, for be it remembered half-stuff is drained and held in drainers to mellow and season so that more. or additional time and power are necessary in the heater in order to retablish the desired and necessary degree of hydration. The hydration of the fibre is an absolute essential in order to form u a sheet of paper on the paper-making machine, consequently any degree of hydration once obtained should be retained until the pulp is formed into paper. This fact is self-evident. Lastly it may be mentioned that time, labor,

' and power are wasted by the use of'the rag cutters, dusters, rotaries or cookers, and drainers which are essential to the old prosess.

I employ in the new process cooking solutions similar to those employed in the old process and which are well known except that such a solution in the present case is in a very dilute state because of the presence in the Hollander engine in which said solution is placed of a larger volume of water than can be contained or worked in a rotary cooker in the old process, and because, furthermore, of the thorough agitation which takes place in said engine. The initially finely cut stock in the rotary cooker takes up more room than the coarser stock in the Hollander engine, proportionately, and the circulation in the former is altogether too slow to be effective.

The steam in my process is introduced into the Hollander engine and preferably.

to an extent only which brings the contents of said engine to a degree of temperature that is just below the boiling point.

The Hollander engine is utilized very largely in the new process. Not only is the steam introduced into the Hollander engine, and previously thereto the cooking solution, but the cooking solution is washed away from said engine, thehard stock is reduced to a pulp therein, and the bleaching and final washing are done therein and therewith. The cooking solution or liquor extracts entirely the sizing, lignin, etc. from the fibre.

The new process will now be described in detail.

New process.

The hard stock is first sorted and the pieces which are approximately a yard square or less are thrown on to an apron conveyor, while the pieces which exceed that dimension are placed in a rag chopper before being delivered to said conveyor. In the chopper the large ieces are cut, by means of a slowly revolving axe knife which shears against a bed knife, into pieces about a yard square, and the pieces so out are dropped from said chopper on to the aforesaid conveyor. In the old process the stock is practically shredded, by means of knives or blades constructed and arranged to that end, into small pieces, with the result that a large amount of lint is produced andthe edges of said pieces are frayed, which en tails a material loss that is obviated by the chopping operation, and by leaving the stock in comparatively large pieces. The stock in the first instance, if of the proper size, and in the second instance, after being large pieces, the amount of waste during the dry-cleaning operation or step in the process is also a negligible quantity. After being dry cleaned the stock is carried to a Hollander engine especially adapted for use 1n the present process.

The equipment of the Hollander engine is of such a nature that the hard stock can therein be cooked and washed, or washed, cooked, and rewashed, cut into or reduced to fine particles, bleached, and again washed, all of which coupled with the novel features of the new process enables one to produce, after only eight hours treatment, a most excellent pulp of a length that can be readily pumped.

From the Hollander engine the pulp is emptied into stuff-chests where it is agitated and held in reserve until supplied to the beaters. This storing of the pulp in a high state of hydration in the stuff-chests may be said to constitute the final step in the new process as a Whole.

The Hollander engine used in carrying out my process, and by means of which said engine becomes a very valuable and important auxiliary element in said process, has a specially constructed beater roll, a washing cylinder covered with (in place of wire mesh, sand grades which are coarser, and sand traps which have an extra large area and are extra deep. More dirt can be removed through #30 than through #60 wire mesh, which is the reason for using the former. The sand grates are 50% coarser in this case, and the sand traps are twice as large in area, and twice as deep, in the Hollander engine which I use than they are in the ordinary Hollander engine, in order to facilitate the dropping of the dirt into the sand traps and enable them to receive and contain all of said dirt, there being dirt here that in the oldprocess would be removed by the rag dusters. The beater roll must have no wood or material in its construction that will not withstand the action of heat and of the chemicals used in the process. This roll revolves in contact with the usual bed plate or bed-plate knife, and is kept in motion from the time the hard stock is first immersed in the water in the Hollander engine until said stock as pulp ready for the-beater is removed from said engine. and during all this time the stock is subjected to the reducing action of said roll, and is at atmospheric pressure in the water.

The first step in the process, so far as the Hollander'engme is concerned, may b'e'that of washing, or it may be that of cookin depending u on the amount of dirt in the hard stock, an to some extent on the nature or character of said stock. Although this preliminary washing is not as a r ule neoessar y, for the purpose ofthis description 1t will be assumed that the stock is first washed, which is done b turning on the wash water to the Hollan er engine, and continuing the washing operation for u Wards of an hour or so long as is require to clean the stock. The wash water is next shut 011' and the water in the en ine allowed to wash down so that the stock circulates freely and properly, the washing down bein effected with the aid of the washing cylinder of the engine which is lowered and caused to dip out the, dirty water and discharge 1t to and through the waste. Fresh water is admitted to the en ine during the time the dirty water is being discharged.

Thebeater roll is revolving meanwhile and continues to revolve until the stock becomes pulp and is removed from the Hollander engine, said roll operating constantly to causethe stock to circulate and also reduce said. stock to an ever increasing de gree of fineness, so to speak.

After the first washlng the stock 18 subjected to the action of the steam and the cooking solution, the former being then turned on to the engine and the latter being introduced into said engine. The cooking solution here is in .a very much more diluted state, on account of the presence of a much larger volume of water, than could be worked in the rotary cooker of the old proce'ss, and of the thorough agitation to which said water is subjected by the beater roll, as hereinbefore pointed out. The following is a comparison of two ordinary formulas forcooking solutions:

For the cook in the Hollander engine (new process)- 16,212 lbs. of water, 1,200 stock,

132 lime, I

1 causticsoda; I For the cook in the. rotarycooker '(old process)-- I 19,437 lbs'. of water, 6,000 stock, 800 lime,

V 1.8 caustic soda. From this will be obtained an idea of the .ratio of dilution of the solutions.

vThe abovednentionedchemicals are well known to those skilled in the art of cook-' ing hard stock. In myprocess I merely cut downthe quantity, as already stated.

thoroughly agitated and circulatedlwiththe after the cookin hard 'stock while the latter is being steamed .apart, not only completely cooks the fibre,

frees the lignin, and leaves said fibre mellow and pliable, but has a decided bleaching efiect or action as well, which is a matter possessing considerable advantage and importance.

Steam is introducedthrou h the side of the Hollander engine preferably at a point about six inches above the floor of the engine and opposite to the end of the mi dteather. And the steam is blown into the engine for about one and one-half hours, when it is shut off. The stock is, now permitted to circulate, always under the impetus or impulsion which the mass in the enine receives from the revolving beater roll, tor about one-half hour in the hot cooking liquor, at the end of which time it is found that the stock is thoroughly cooked and the lignin separated from the fibre, all without bringing the contents of the engine to the boiling point.

The rewashing or second washing, Where there has been a previous washing as in the present example, follows the cooking, andthis is accomplished with the aid of the washing cylinder. Except when in use the washing cylinder is in elevated and inactive position, but when in use said cylinder is lowered to dip out the dirty water, as pre viously explained, fresh water being admitted to the engine at the same-time the dirty water is being discharged. This washing is continued until the cooking liquor is all washed away and a very bright, well cookedpulp is obtained, which is ready to' be bleached. Some three hours are usually removal of the cooking solu-' required for the ,tion.

The term pulp appliedin the preceding paragraph to the stock is used advisedly because said stock has by this time been reduced to a pulpy condition by the action of the beater roll operating against the bed knife of the engine, by the disintegrating action of the cooking liquor, and by the circulation, it having then been worked out of the rag and into a fibrous state.

The continual admissions of fresh water to the engine, during the washing operation operation, washes away through the was ing cylinder the cooking liquor, and with it the lignin, natural coloring matter, and sizing agents, leaving a a bright pulp which can readily be bleached with chloride of lime, a less quantity of said lime being required than with the old method of cooking in the old process.

Next to the final operation or step of the process in the Hollander engine is that of bleaching. This is accomplished with the usual bleaching liquor whichis introduced into the circulating mass of pulp in the engine, after the cooking liquor has beenwashed away. The action of the bleaching liquor is similar in this case to that in a case under the old process, except that a less quantity is needed, and a better intermixture of the pulp and liquor is made possible, for reasons already plainly set orth. The bleaching operation takes but a comparatively short time.

The final operation or step in the H01- lander engine is that of washing the bleaching liquor from the pulp, or, in other words, in rewashing said pulp. This is done in a manner similar to that previously described in full, the washing cylinder being employed as upon the other occasions. All of the above-described steps which take place in the Hollander engine occur while the stock is in water at atmospheric pressure, as previously observed.

As a final step in the process the pulp prepared in the manner hereinbefore set forth in detail is pumped or otherwise introduced into a stuff-chest or -chests and left until needed in the actual process of making paper.

The new process all'ords complete control of the hydration of the fibres, inasmuch as they are held in suspension in water from start to finish of the process after the Hollander engine is reached. In cooking under pressure in the old process, and draining under the rotary cooker and again in drainers, the water leaves the fibres, and when they are again placed in solution the hydra tion is not nearly so easily controlled. Under the new process the fibres contain a surplus of water all through the washing before cooking, if that step be included, the cooking, the washing after cooking, the bleaching. and the washing after bleaching, or right up to the time the stock or pulp is emptied into the stuff-chest. and even until said pulp is pumped into the beater to be thickened for the final treatment in the beater and refiner.

The hard stock, surcharged with water and protected by a viscosity produced by a combination of water and fibre elements, to restate an important and vital fact connected with the new process, and thus reduced to a pulp in a mushy state, is stored as just explained in the stuff-chests until needed, when said pulp is pumped into the beater engine, the washing cylinder of such engine being utilized to make the furnish as dry, comparatively and technically speaking, as may be desired. From the beater engine the pulp goes to the cylinder or Fourdrinier paper-making machine. A pulp in an ad vanced stage of hydration is produced by my process, not only without confining the stock under pressure, but without directlyapplied manual labor after the stock is fed to the Hollander engine.

By providmg several Hollander engines which are especially equipped for use in my process, and stuff-chests and pumps located in the basement under said engines, each of the latter can be loaded with a separate kind of hard stock and given proper chemical treatment, after which any desired blend may be made in the beater engine. Thus, for example, in a mill provided with six Hollander engines, two could be run on jute, and four on rope, makinga furnish in the beater which would consist of one-third jute and two-thirds rope.

My hard-stock pulp remains in a slush staltle like soft-stock pulp handled in a Wood m1 Caustic soda and carbonate of lime have been applied to stock in a Hollander engine for the removal of ink from old papers, but not for cooking hard stock, and so far as is known lime has never been used in a Hollander engine for any purpose.

It will have been noted that the cooking, (omitting a previous washing which experience has shown to be seldom needed),

washing, bleaching, and rewashing steps take place in the Hollander engine in the sequence named, while what may be termed the combined step of reducing by a cutting action the hard stock and agitating and circulating the contents of said engine is continuous throughout the period covered by said sequence, wherefor it may be said that the four comparatively short, sequential steps performed in said engine are embraced by, or interposed or interspersed in a long, fifth step. In this peculiar combination of steps reside most valuable and important features. It is by them that the hard stock is cooked and bleached, with the necessary subsequent washing away of the dirt, waste, and solution in each case, and reduced to the required degree of fineness, and at the same time hydrated and maintained in a state of hydration, so that no subsequent hydration, as would be needed in the event the stock were allowed to become dry before being stored in the stuff-chests, is demanded.

Never before my invention have large pieces of hard stock been placed in a Hollander en ine and thereln, in water at atmospherlc pressure, cooked, bleached, washed, and reduced to pulp, and this all in one continuous process. Never before has hard stock been handled in large pieces even from the start, but on the contrary it has been reduced to small pieces as soon as it was sorted. In this and other particulars the present invention is Widely different from the rior art, as well as being economical and hlghly efiicient.

Obviously, when the hard stock consists of rope, the same cannot be cut into pieces which may approximate a yard square, but it can be and is cut into corresponding lengths and these lengths or long pieces are put through the process tjust as is the hardstock when in pieces 0 tively speaking. I

The term hard stock is used herein and in the a pended claims in its technical sense, as usually understood by paper manufacturers, to define a paper stock from rags and like materials, such as burlap, gunny, rope, jute, hem and sisal, and as distinguished from w at is technically known as soft stock consisting of sulphite, sulphate, ground wood, and old papers.

What I claim as m invention, and deslre to secure by Letters atent, is-

1. The process of converting hard stock into half stock, in the manufacture of paper, which comprises introducin the stock, together with the re uired chemicals and a considerable body 0 water, into a suitable reducing engine and therein cooking itat large area, 7 relaatmospheric pressure in the water while subjecting it to the action of a beater roll.

2. The process of converting hard stock into half stock, in the manufacture of paper, which comprises dry cleaning the stock and introducing it, in its varying commercial sizes up to about one yard without cutting, into a suitable reducing engine and therein cooking it at atmospheric pressure in a considerable body of water while subjecting it to the action of a beater roll.

3. The process of converting hard stock into half stock, in the manufacture of paper, which comprises cooking, washing, bleaching, and rewashing the stock at atmos heric pressure while subjecting it to the act1on of into half stock, in the manufacture of paper,

WhlCh comprises taking the stock in com- I mercial sizes, cut onl when in sizes upwards of about a yar in length, and bo11-' ing, washingbleaching, and rew'ashing it 'atatmospheric pressure while subjecting it to the action of a beater roll and in the presence throughout of a quantity of water sufiicient to hydrate and to prevent dehydration of the fibers. Va

5. The process of converting hard stock into half stock, in the manufacture of paper, which comprises introducing the stock into an engine of the Hollander type, open to the pressure, While subjecting it to the beater action of the engine, and in the presence of a quantity ofwater suflicient to hydrate its fibers.

7. The process of converting hard stock into half stock, in the manufacture of paper,

which comprises introducing the stock into an engine of the Hollander type and, while it is being beaten up therein and before its removal therefrom, cooking, washing, bleaching, and rewashing it at atmospheric pressure and in the presence of a quantity of water sufficient to hydrate its fibers, and thereafter maintaining the converted stock sus ended in water sufiicient to prevent dehy ration of the fibers until ready for beat-. mg.

' GEORGE L. BIDWELL.

Witnesses:

HENRY N. GRIFFIN, WARREN M. BROTZMAN. 

